There is a growing demand for vending machines which dispense both hot and cold beverages made from fresh ingredients. Different approaches have been taken to protect the ingredients in the dispenser. One approach is the storage of bulk concentrate which is discharged into a cup as needed and water is added. The drawbacks with this approach are, the constant atmospheric contact with the concentrate with consequent increase of moistness and loss of flavour, and the variance of the amount of concentrate discharged into each cup.
A different and newer approach has been to provide stacks of beverage concentrate-containing foamed thermoplastic cups stored for dispensing by vending machines, each cup containing a premeasured amount of beverage concentrate. A wedging action holding the upper up in the lower cup is supposed to seal the comestible from the atmosphere (see U.S. Pat. No. 4,096,947, for example). However, that is not the case as no effective seal is provided.
In another attempt to protect the comestible from the atmosphere, U.S. Pat. No. 4,156,483 (Day) teaches, in a stack of expanded or foamed polystyrene vending cups (each cup having a wall thickness typically in the range of 1.0 to 3.0 mm), containing a comestible between adjacent cups, the use of an angular lug on the outer surface of the cup at the bottom, and a like angularly shaped groove having an entry ramp on the inside of the cup terminating at a radially extending upwardly facing sealing ledge or surface. In use, the upper cup is pushed into a lower cup so that when the lug enter the groove, the entry ramp allegedly engages the upper surface of the lug and forces the bottom of the lug to seat on the ledge to seal the space between the cups. In other words, the entry ramp of the groove is alleged to push against the sloped upper portion of the lug to cause the bottom of the lug to seal against the upper surface of the ledge when the lug is in the groove and seats on the ledge. The difficulty with this approach is the material being worked with. The expansion of the polystyrene beads is uneven. If the groove is oversized or the lug undersized there can be no seal. If the groove is undersized or the lug oversized because the sealing action proposed by Day in his U.S. Pat. No. 4,156,483 (see FIGS. 1, 3, 6, 8, 9 and 10) is purported to be in the axial direction, there is not adequate allowance for compressed material and the cups will have a tendency to separate as the lug and groove naturally try to assume their original separate configurations and dimensions. Additionally, the fused and expanded bead material is subject to cracking and chipping when overly stressed, breaking off and falling into the cup.
German Pat. No. 2,639,929 teaches the use of a circular lug on the outer surface of the cup at the bottom and a like shaped circular groove on the inside wall of the cup. In use, an upper cup is pushed into a lower cup until the lug enters the groove sealing the space between an upper add lower cup.
With regard to the structure shown in FIG. 4 of U.S. Pat. No. 4,156,483, a "&lt;-shaped" lug on the outer surface of the cup at the bottom and a like shaped "&lt;-shaped" groove on the inside wall of the cup are provided as part of the proposal for receiving the "&lt;-shaped" lug of a like upper cup.
Once again the difficulty with these last-mentioned approaches is the material Manfred Rothkegel and Day are working with. The expansion of the polystyrene beads is uneven and the fused and expanded material is subject to cracking and chipping when overly stressed, breaking off and falling into the cup.
Because it is impossible from a practical point of view to consistently manufacture equally sized lugs and grooves, the purported "equally sized grooves and lugs" cannot provide an effective seal. If the lug of one of a pair of ups is larger than the groove of the other cup it is being forced into, the cups will tend to "pop" apart as the compressed expanded thermoplastic material resumes its original configuration and dimensions, thus preventing a seal. If the lug is of the same configuration but smaller than the groove, there will be no seal between the two cups.
With respect to the manufacture of the Day lug, the lug profile must be cut into the female mould cavity in order to manufacture the cup. Cutting angular grooves into the mould causes notch-type stress concentrations and subsequent failure when the mould is stressed during operation. While this problem can be overcome by making the mould cavity thicker, this increases the operating cycle time. The problem could also be overcome by using a two-part cavity but this modification significantly increases mould cost.
Not only must the lug enter the groove without breaking or being compressed beyond its ability to restore, it must be easily dislodged Therefrom. In many instances, part of the lug is broken off and falls into the beverage liquid.
Therefore, for a cup to be a truly locking and sealing cup when inserted one into the other for sealing the commestibles carried at the bottom of the lowermost cup by a lug carried by one of the cups entering a groove in the other cup, the cups when nested must accommodate the compressed material between the lug and groove, must not overcompress the material of the lug and groove to be able to resume their original configuration for sealing the space between the nested cups, the seal must be complete yet the cups must easily separate without breakage of material from the lug and the cups must be able to seal and separate at least three times during manufacture and dispensing without damaging the material of the lug.
It is therefore an object of this invention to provide an improved foamed thermoplastic cup having an improved lug and groove configuration which overcomes the aforementioned difficulties of the prior art proposals, is easily manufactured at minimum cost, and provides an effective seal between two like cups when nested together yet provides such effective seal between the two cups in a manner that the lowermost cup may be easily dislodged from the upper cup by axial downward force on the rim of the lowermost cup.
Further and other objects of this invention will be realized by those skilled in the art from the following summary of the invention and detailed description of an embodiment of the invention.